In recent years, electrophotographic photosensitive members each having a photosensitive layer containing an organic charge generation substance and an organic charge transport substance (organic electrophotographic photosensitive members) have been vigorously used for electrophotographic apparatuses such as a copying machine and a printer. Photosensitive layers each having a laminated (forward-laminated) layer configuration have been in the mainstream of such photosensitive layers from the viewpoint of durability, the photosensitive layers each having a laminated (forward-laminated) layer configuration being obtained by laminating a charge generation layer containing a charge generation substance and a charge transport layer (hole transport layer) containing a charge transport substance (hole transport substance) on the side of a support.
Of the charge generation substances, a charge generation substance having sensitivity in a red or infrared region is used for an electrophotographic apparatus to be mounted on, for example, a laser beam printer that has remarkably developed in recent years, and the frequency at which such a charge generation substance is demanded is increasing. Known examples of a charge generation substance having a sensitivity in an infrared region include: phthalocyanine pigments such as oxytitanium phthalocyanine, hydroxygallium phthalocyanine, and chiorogallium phthalocyanine; and azo pigments such as monoazo, bisazo, and trisazo pigments.
However, when a charge generation substance having high sensitivity is used, there arises a problem in that the amount of charge to be generated is large, an electron after injection of a hole into a hole transport layer is apt to reside in a charge generation layer, and a memory is apt to occur. To be specific, a so-called positive ghost in which the density of only a portion irradiated with light at the time of forward rotation in an output image increases, or a so-called negative ghost in which the density of only a portion irradiated with light at the time of forward rotation in an output image decreases is observed
As a conventional technique for suppressing such ahost phenomena, JP-A 11-172142 (Patent Document 1) and JP-A 2002-091039 (Patent Document 2) each disclose a technique involving the use of type-II chlorogallium phthalocyanine as a charge generation substance, JP-A 07-104495 (Patent Document 3) discloses a technique involving incorporating an acceptor compound into a charge generation layer using oxytitanium phthalocyanine, JP-A 2000-292946 (Patent Document 4) and JP-A 2002-296817 (Patent Document 5) each disclose a technique involving incorporating a dithiobenzyl compound into a charge generation layer using phthalocyanine, and JP-A 02-136860 (Patent Document 6), JP-A 02-136861 (Patent Document 7), JP-A 02-146048 (Patent Document 8), JP-A 02-146049 (Patent Document 9), JP-A 02-146050 (Patent Document 10), JP-A 05-150498 (Patent Document 11), JP-A 06-313974 (Patent Document 12), and JP-A 2000-039730 (Patent Document 13) each disclose a technique involving incorporating an electron transport substance, an electron accepting substance, or an electron aspirating substance into a charge generation layer.    Patent Document 1: JP-A 11-172142    Patent Document 2: JP-A 2002-091039    Patent Document 3: JP-A 07-104495    Patent Document 4: JP-A 2000-292946    Patent Document 5: JP-A 2002-296817    Patent Document 6: JP-A 02-136860    Patent Document 7: JP-A 02-136861    Patent Document 8: JP-A 02-146048    Patent Document 9: JP-A 02-146049    Patent Document 10: JP-A 02-146050    Patent Document 11: JP-A 05-150498    Patent Document 12: JP-A 06-313974    Patent Document 13: JP-A 2000-039730